Filament production for synthetic linear polymers



March 25, 1969 s. a. HENDRY; JR 3,435,108

FILAMENI PRODUCTION FOR SYNTHETIC LINEAR POLYMERS Filed Sept. 11, 1967 Sheet of 2 A/A Fww GEM INVENTOR F/G. 1 BY ATTORNEY March 25, 1969 G. G. HENDRY, JR 3, 35, 0

FILAMENT PRODUCTION FOR SYNTHETIC LINEAR POLYMERS Filed Sept. 11, 1967 Sheet 2 of 2 I IIIIIA 'lIIIlIIIII/IIIIM/ ROTOM ETER GAS - I NVENT OR I BY F/G. 2

United States Patent 3,435,108 FILAMENT lRODUQTION FOR SYNTHETIC LINEAR POLYMERS Glenn G. Hendry, J12, Shelby, N.C., assignor to Fiber Industries, Inc, a corporation of Delaware Continuation-in-part of application Ser. No. 398,330, Sept. 22, 1964. This application Sept. 11, 1967, Ser. No. 667,333

Int. Cl. 1328b 3/20 US. Cl. 254176 4 Claims ABSTRACT OF THE DISCLOSURE A method for increasing production rates of a melt spinning operation for synthetic linear polymeric filamentary material comprising dividing a filamentary extrudate into at least two separate portions and then subjecting the divided filamentary material for short time intervals to a nonturbulent cooling gaseous medium.

This invention which is a continuation-in-part of United States patent application Ser. No. 398,330 filed Sept. 22, 1964, and now abandoned relates to a process for melt spinning filaments for synthetic polymers. More particularly, the invention is directed to a unique method for substantially increasing production rates of a melt spinning operation for synthetic linear polymeric filamentary material.

The known procedure for producing melt spinning filament from polymers such as polyesters, polyamides, and polyolefins includes the extrusion of molten polymer through a filter and a spinning plate containing the identical number of orifices required to provide the desired number of filaments in the yarn product. Under these conditions, if a change in the number of filaments of the produced yarn is required, a different type of multihole spinneret must be installed for the operation.

A unique proces has been discovered wherein a multihole spinneret can be utilized and portions of the main threadline can be divided to obtain the desired number of filaments in separate yarn products thereby increasing production rates without any detrimental effects in physical or chemical properties in the resulting yarn products. The process of the invention which includes a combination of steps, is achieved by initially extruding synthetic linear polymeric filamentary material through a spinning plate containing a plurality of orifices. Immediately after the extrusion, the filamentary material is divided in at least two separate portions while passing through an insulated portion from the ambient atmosphere for a distance from about 2 inches to about inches from the spinning plate. After the divided filamentary material has passed through the insulated portion, a cool gaseous medium is contacted with the filaments so that the filaments are uniformly cooled at a rate to avoid a turbulence effect of the filaments. At this point, the separated filaments can be collected to be placed on a bobbin, roll, etc. or forwarded to other processing steps.

As is known, a single yarn product can be melt spun from a multihole spinneret and cooled in the ordinary surrounding atmosphere to provide a highly satisfactory filament yarn. Following this process, however, and dividing a portion of the filament threadline wherein each portion is collected separately, the resulting products were found to have an undesirable short term denier variation with a high break and wrap level as well as an undesirable streaky appearance. In order to overcome these disadvantages and to utilize a divided threadline operation to increase production rates, the divided extruded filaments were immediately passed through a chamber which acts as an insulator from surrounding ambient temperatures as well as msicellaneous air currents and exposed under controlled conditions by exposure to a cool gaseous medium. Following the procedure of this invention, several highly satisfactory yarn filament products can be produced simultaneously from one multiholed spinneret in quantities which can double, triple, etc. the normal production rates of the known procedures. An added advantage of the process of this invention relates to the fact that two diiferent yarn products, i.e., the number of filaments such as a 40 filament yarn and a 70 filament yarn, can be produced simultaneously having the desired physical properties of a satisfactory yarn.

The synthetic linear polymers which can be used in the process of the invention to produce the desired filamentary material include polyesters, especially poly(ethylene terepthalate) polymers, copolyesters, polyamides, especially poly(hexamethylene adipamide), copolyamides, polyolefins, especially isotactic polypropylene and copolyolefins. The polymeric materials which are utilized must have intrinsic viscosities which are fiberforming and produce fibers useful in the textile and industrial fields.

The polymers are extruded through multihole spinnerets wherein the orifices in the spinning plate are arranged in any convenient manner suitable to divide the threadline after the extrusion. The arrangement of the orifices in the spinning plate is not necessarily critical and the openings of the spinneret can be arranged in parallel rows, crescent, semicircular or circular formations and the like, whichever may be desired. It is essential, however, that a multiplicity of orifices are present in the spinning plate and it is preferred to have 10 to 1,000 orifices available, depending on the type of filament to be prepared and the number of divided portions of the threadline desired.

The extruded filaments can be divided by various known means and the division is readily apparent as the filaments proceed from the spinneret. The type of division can be made in equal portions or unequal portions of the threadline as well as dividing more in 2 portions such as 3 to 6 divisions, if desired. A typical means of division of the filaments can be accomplished by taking portions of the threadline and directing them to the various collecting means. The division of filaments becomes more pronounced as the filaments proceed through the process. For example, it is highly desirable to have the minimum amount of division as the filaments pass through the insulated portion and the contacting of the filaments with the cool gaseous medium to provide a uniform cooling treatment of the filaments. After the filaments have been treated, the divided filaments can be separately converged into a more compact form for surface treatment with an appropriate treating agent such as antistatic agents, lubrication and the like, and for collection on a bobbin, roller or the like.

The insulating portion immediately adjacent the face of the spinning plate completely encircles the spinning plate and insulates the freshly extruded filaments from the ambient atmosphere. Although it is not definitely known, it is believed that the purpose of the insulator is to control the cooling rate of the extruded filaments. The length of insulation portion can range from about 2 inches to about 20 inches, depending on the denier and/or number of the filaments, speed of spinning, and the like. In general, as the denier of the filaments increases, the longer insulation area is desirable and in contrast, the lower the filament denier, the shorter the insulation portion is required. For normal textile fibers, having filament deniers in the range of from 1 to 10, an insulation portion from 2 to 12 inches from the spinneret plate is preferred. It is undesirable to utilize an insulation portion less than 2 inches from the spinneret plate to avoid excessive and detrimental cooling of the spinneret plate.

After the freshly extruded filaments have passed through the insulation portion, the filaments are contacted with a cool gaseous medium in such a manner as to obtain uniform cooling of all the filaments. While the use of gaseous cooling mediums to quench freshly extruded filaments are known as evidenced by United States Patents No. 3,100,- 675 and 2,252,648, the exposure time of filaments to gaseous cooling mediums in the patented processes are extremely long. The long residence time is due to either the slow running speeds of the yarn or the long physical dimensions of the cooling chamber or combinations of both. In the process of this invention, it has been discovered unexpectedly that the residence time of the yarn in the gaseous cooling medium must be quite short. The residence time for polyester yarn in the gaseous cooling medium must be from of a second to of a second and preferably from of a second to of a second. According to the process of this invention, it is also essential that the cooling gaseous medium be presented to the filaments in a manner which avoids any type of turbulence, i.e., the gaseous cooling medium must not physically disturb the separated threadlines. The rate of gas flow required is dependent on several factors, such as number of filaments, filament denier, rate of extrusion and angle of the gas flow to the filaments. In the spinning of textile yarns, the gas flows substantially at right angles to the filaments in the range between from to 25 cubic feet per minute has proven satisfactory. The length of threadline exposure to the cooling gas medium can range from about 0.5 inch to inches, depending on the type of filaments being spun. When polyester is being spun, the length of threadline exposure to the cooling gas medium is from 0.5 inch to 2.5 inches and preferably about 1.5 inches. It should be understood that the running speeds of the yarn, the gas flow and the length of exposure must all be adjusted so as to quench without physically disturbing the separated threadlines.

A better understanding of the invention as well as an appreciation of the criticality of the process parameters may be had from the drawings wherein:

FIGURE 1 is a graph plotting percent U (Uster reading) against air flow in cubic feet per minute for polyester yarn and;

FIGURE 2 is a schematic illustration of the apparatus utilized in a preferred embodiment of this invention.

The Uster Evenness Tester, as used herein, is a device for determining the irregularity of the weight per unit length of filamentary yarns. The Uster Evenness Tester Model C was used in the tests hereinafter disclosed in this application. A complete description of this device is given in the Uster Manual for Evenness Testing issued by the manufacturerZellweger, Ltd, Uster, Switzerland-and a brief description along with the particular applications employed in this patent request are discussed below.

The Uster Evenness Tester measures difierences in dielectric of a material passing through the plates of a condenser. Differences in mass along the length of a fiber to be tested produce changes in a dielectric strength between the condenser plates and these cause variations in frequency of the condenser circuit which are transformed into voltage variations. The instantaneous voltage signal is fed to a recorder and also an integrator which provides a visual indication of the average mass fluctuation and thus denier of the fiber between the condenser plates and computes the total variability in relative units over the period of time the sample passed through the device.

The sample length over which the average fluctuations are measured is dependent on the test conditions and includes yarn speed, condenser plate length, and whether or not a time delay circuit is employed to average out the instantaneous voltage signals. The condition in the examples disclosed herein are Inert Reading at yards per minute yarn speed and Normal Reading at 25 yards per minute yarn speed. The Inert setting which involves the time delay circuit measures an average sample length of approximately 5 feet at the 25 yards per minute speed of advance of the yarn and the Normal setting which does not involve the time delay circuit measures an average sample equal to the length of the condenser plates which is 17 mm. The continuous fluctuations from these sample lengths are then integrated over a yard continuous length of yarn to obtain a total variability. The valves reported in this application are averaged variabilities from several representative bobbins. Thus the Inert values reported represent the average denier variability based on a continuously integrated 5-foot sample length and the Normal values represent the average denier variability based on a continuously integrated 17 mm. sample length.

Turning to FIGURE 1, the criticality of air flow is graphically illustrated. The yarn employed in collecting data for the graph was 70 denier 36 filament spun polyester yarn processed according to the divided thread inflow quench process of this invention, the data being as given in the following table:

Flow rate in Percent in cubic feet Birefringence shrinkage Uster normal per minute As can be seen for the illustrated 70 denier 36 filament yarn, an increase in air flow in excess of 8 cubic feet per minute produces turbulence which creates yarn variations while an air flow of less than 8 cubic feet per minute does not produce a satisfactory quench and again results in higher yarn variations. It should be understood that the illustrated criticality of air flow is dependent on residence time in the quench zone which is, of course, determined by yarn running speeds and the length of the quench zone.

FIGURE 2 of the drawings which is an illustration of the apparatus utilized in a preferred embodiment further clarifies this invention. The melt is extruded through a spinneret 11 from a conventional melt supply container 1%. Upon extrusion, the divided extruded filaments 13 are passed through an insulated portion 12 which surrounds the upper end of the chamber 9 adjacent to the spinneret. At the bottom of the chamber 9 is an air diffuser 14 supplied by a cooling gas supply 15 into the air chamber 17 The cooling gas contacts filaments 13 in such a manner as to avoid any turbuleance effects. The bottom of the chamber 9 is open to the atmosphere and the filaments 13 are then converged to pass over a finish applicator roll 16 to apply the desired finish. From the applicator roll 16 the individual filament bundles can be collected on a bobbin not shown or can be forwarded to other processing steps. It should be understood that other modifications within the scope of this disclosure can be made to the accompanying drawing.

The type of construction for the entrance of the cooling gas medium can be sintered steel, sintered bronze, porous earthenware, perforated metal sheets or tubes and the like. The cooling gas medium can be directed from the outside toward the threadlines to be cooled or from the inside of the threadlines. It is essential however, that the cooling stream uniformly contacts the filaments to be cooled. The cooling gas medium which is used can be any inert gas such as air, carbon dioxide, nitrogen, and the like, maintained at temperatures to provide the cooling effect. The preferred cooling gas is air at ordinary temperatures for example, room temperature.

Aftert he extruded filaments have been treated, the individual separated filament bundles can be contacted with a suitable textile surface finish, if desired, and collected on a bobbin, roller, etc. or immediately forwarded to other processing steps.

The following examples will further illustrate the process of the invention Without limiting the same:

EXAMPLE 1 Poly(ethylene terephthalate) polymer having an intrinsic viscosity of .60 is melted by means of a screw melter and the metered quantities of molten polymer are pumped through a sand filter and spinneret maintained at a temperature of 280290 C. having 72 round holes arranged so as to conveniently divide the threadline into 2 separate portions. Each separate threadline has a total spun denier of 231. The separate threadlines are passed through an insulated portion having a depth of 6 inches from the spinneret. The threadlines are then uniformly contacted for seconds with an air flow of 12 cubic feet per minute from a circular porous metal air diffuser 1 /2 inches in depth surrounding the threadlines. At this rate of air flow, there is no visible turbulence of the threadlines. The air contact is at a 90 angle with the threadlines. The separate threadlines are then converged to pass over individual applicator rolls to apply the desired finish and collected on a bobbin for further processing. The yarn products had a uniformity of .65 of an inert percent U Uster reading.

EXAMPLE 2 In an manner similar to Example 1, except that the divided filaments are extruded into the atmosphere without utilizing the process of this invention, the yarn products have a uniformity of 1.43 of an inert percent U Uster reading.

The comparison of Examples 1 and 2 clearly demonstates the improvements obtained by the process of this invention.

In a similar procedure as described in Example 1, poly- (ethylene terephthalate/sebacate) (intrinsic viscosity 0.47) is extruded through spinnerets maintained at temperatures of 250-255 C. A highly satisfactory uniform yarn product is obtained. Similar results are obtained by the procedure of Example 1 utilizing isotactic polypropylene (melt index 23.2) and poly(hexamethylene adipamide) (relative viscosity 34) extruded through spinnerets maintained at temperatures of 270-280 C.

It is to be understood that the foregoing description is merely illustrative of preferred embodiments of the invention of which many variations may be made by those skilled in the art within the scope of the following claims Without departing from the spirit thereof.

Having thus disclosed the invention What is claimed is:

1. A method for substantially increasing production rates of poly(ethylene terephthalate) filamentary material which comprises the steps, in combination, of extruding said polymeric filamentary material through a spinning plate containing a plurality of orifices, dividing said filamentary material in at least two separate portions while passing said divided portions through an insulated portion from the ambient atmosphere for a distance from about 6 inches to about 20 inches from said spinning plate, thereafter passing a cooling gaseous medium for a residence time of from of a second to of a second against said divided filamentary material so as to cool uniformly all of said filamentary material.

2. The process of claim 1 wherein said cooling gaseous medium is employed for a residence time of from of a second to ()0[) of a second.

3. The process of claim 1 wherein the cooling gaseous medium is employed at a fiow rate of from about 5 to about 25 cubic feet per minute.

4 The process of claim 1 wherein the cooling medium is air.

References Cited UNITED STATES PATENTS 2,252,684 8/ 1941 Babcock. 3,056,711 10/1962 Frickert 156-163 X 3,100,675 8/ 1963 Westerhuis et al. 3,320,343 5/1967 Buschmann et 8.1. 3,346,684 10/ 1967 Gosden.

JULIUS FROME, Primary Examiner.

J. H. WOO, Assistant Examiner.

US. Cl. X.R. l8-8; 2642l0 

